As disclosed in U.S. Pat. No. 4,036,887 (Sheldon et al.), 3-bromobenzaldehyde is useful as an insecticide precursor and can be prepared by reacting benzaldehyde with bromine chloride in the presence of aluminum chloride and about 140-500 ml of a chloroalkane, such as dichloromethane, 1,2-dichloroethane, or chloroform, per mol of benzaldehyde. This process has advantages over other known techniques of synthesizing 3-bromobenzaldehyde, but it also has disadvantages. Specifically, the process of Sheldon et al. leads to the formation of as much as 5% of 3-chloro derivatives, thus reducing the efficiency of the process and making product isolation more difficult. Also, the use of 1,2-dichloroethane, the preferred solvent of Sheldon et al., leads to the formation of 1,2-dibromoethane, a toxic material which is undesirable even in trace quantities and the formation of which complicates product isolation and aqueous waste disposal.